Depends how the Wacht am Rhein forces are used. If they attack in December against the Soviet forces in Poland before they attack in January, the disparity of forces probably doesn't end well for a German pre-emptive offensive. I think it is likely that Hitler would have an earlier Operation Spring Awakening in Hungary to try and shore up the positions there, namely to defend Budapest from the coming Soviet offensive and secure Hungary and it's oil. That is perhaps the one place they could actually have achieved an operational success in late 1944-early 1945, as they would have a decent correlation of forces compared to the Soviets, have fresher forces, if they used Bodenplatte forces they'd have air superiority, and potentially they'd have surprise on their side. Plus it was largely outside the area the Wallies focused their strategic bombing on, so supply lines would be good. The Soviets on the other hand have their logistics constrained by the shift in rail gauge and supply lines through the Carpathians. They were also a bit overextended at the time and it took them nearly two months to encircle Budapest after launching their October offensive against Hungary; they could be in a position to be smashed up and checked or potentially even driven back.
As this is before the Yalta Conference, Stalin's forces failing to secure Budapest and perhaps being pushed out of a lot of Hungary, even as the Vistula-Oder offensive was to begin, could well result in a different agreement. Depending on what happens down the road the Wallies could advance more quickly and secure Austria and the Czech parts of Czechoslovakia first as well as parts of Hungary, which really changes the fall of borders post-war, especially if Wallied forces get to Yugoslavia or at least portions of it first. Perhaps the Wallies can reach Berlin around the same time as the Soviets, but who knows if the Wallies will even bother, perhaps they focus more on Austria/the Balkans/Hungary? If the Germans do really manage to inflict major damage to Soviet forces in Hungary, that would really prevent them from at least reaching Austria by the end of the war and may well force the Soviets to move forces from Poland to Hungary to make up for their losses, taking steam off of their main push on Berlin.